Page 69 - 2022 Spring JSOM

Discussion deployed to the forward environment and able to be employed
by non– specialty-trained medical providers.
In this study, we assessed the function of a simplified device
as a transport ventilator during ground transport when used Transport of critically ill patients represents an inherent risk,
as an adjunct to ECLS in a large-animal model of combat-rel- with transports potentially leading to patient complications
evant trauma. The data here represent intra- and interfacility and death. 23,24 Movement of critical patients has resulted in
ground evacuation only; the larger experimental data set is more than two unplanned events per transport, 46% of which
reported elsewhere and involved clinically relevant ICU con- were device related. 24,25 This highlights the importance of hav-
ditions, making the transports used in this study similar to ing safe and reliable equipment for all patient moves, even
human interfacility transports. 6,7 when those moves are conducted after care-in-place at or near
the point of injury has been ongoing for days. Our study in-
The SAVe II was able to provide adequate ventilation for our vestigated these aspects, and we did not experience any un-
animals during all phases of transport when used in an adjunc- planned events during the 33 transports we completed. We
tive mode to ECLS. This concept of adjunctive use of ventila- also did not identify any degradation in animal clinical status
tors with various forms of ECLS was previously introduced while using the SAVe II. Our findings suggest that simplified
by our group for potential applications during prolonged critical care equipment is a potential choice for respiratory
field care and aeromedical evacuation. 7,13 This approach can support of casualties, specifically when used as an adjunct to
mitigate ventilator-induced lung injury and provide for lung- ECLS, as tested in our current study.
protective or lung-rest protocols while ECLS offloads the lung
requirements for CO removal and oxygenation. This concept Our transport times were, on average, less than half the mini-
2
is potentially the next phase in advancement of both aero- mum time on scene of the assessment done by Phillipp et al.
26
medical evacuation and care at or near the point of injury, testing ECLS during transport (90 to 180 minutes ). The time
26
where both casualty stability and optimization of care may be to get a trauma patient to critical care in combat operations
achieved concomitantly. Of note, the highlights of the SAVe ranges from 35 to 50 minutes, 27,28 putting our experimental
II as tested are its light weight and cube shape rather than transport times in line with what has been experienced during
the functions of a fully capable ventilator; thus, any benefit of recent armed conflicts.
ventilator-induced lung injury reduction must be placed on the
ECLS if such limited devices as the SAVe II are used. The device was previously tested in swine with acute lung
injury for a short duration, where it was shown to be able
We determined the simplified ventilator to be suitable for to provide support for 1 hour after oleic acid–induced lung
mobile critical care. During intra- and interfacility transport, injury. The SAVe II does not display patient feedback, such
29
including building, elevator, and open road, we did not in- as measured exhaled tidal volume (and thus, by extension,
cur ventilator-related complications or malfunctions. We saw also does not display minute ventilation, either delivered or
sporadic significant changes in PIP, mean arterial pressure, exhaled), airway pressures, or graphic scalars, data that are
minute ventilation, end-tidal carbon dioxide (mmHg) (etCO ), unlikely to be useful in the field by inexperienced providers
2
and PFR, although none can be tied solely to the use of the but that may limit the versatility of use of the device by more
device; rather, as in all critical care, the changes seen result highly trained personnel.
from many factors. The numerical changes we saw between
pre- and post-transport data were clinically insignificant. We Our study found that the device provided lung-protective ven-
determined adequate performance of the SAVe II as part of the tilation (V , 5–8mL/kg) at all times. We were able to maintain

critical care tool set when it is used as an adjunct to venove- minute ventilation of approximately 50% of baseline values
T
nous ECLS. Following injury on day 2, all animals required when the SAVe II was used as an adjunct to ECLS (data not re-
increased Fio while in the ICU, and thus received increased ported; Table 1). Our day 1 animals were slightly overventilated
2
Fio , as described above during transport.
2 because extracorporeal therapies, such as the ECLS used here,
are not designed for application in healthy, uninjured states.
Airway management is the second leading cause of poten- After injury on day 2, we saw acid-base imbalance more reflec-
tially survivable injury in combat and an independent mor- tive of typical patients with acute respiratory distress syndrome
14
tality risk in the combat wounded, and manual ventilation (ARDS) (Table 2). The study animals were in mild ARDS after
15
delivers inconsistent results. 16,17 In a targeted review of for- injury (PFR < 300) and had severe metabolic derangements
30
ward-deployment lessons learned, 30% of recommendations (elevated lactate and base excess; Table 2) seen in combat ca-
for improvement directly mention airway management skills, sualties, again highlighting the relevance of our injury model.
18
and a recent prolonged field care clinical practice guideline However, it is important to remember that our testing occurred
highlights that although artificial ventilation is better than no along with ECLS. Thus, in our model, the SAVe II performed
ventilation, the level of training required to effectively use MV adequately, but more stringent testing is warranted to assess
presents challenges. Thus, development of small portable standalone performance of such simplified tools.
19
ventilators is a logical evolution in the care of wounded Ser-
vicemembers. Complete air superiority in recent conflicts en- The limitations of the SAVe II presented a challenge on one
abled US Forces and their allies expedient, often unrestricted, occasion during this study, where the animal had low arterial
air lift with a mean evacuation time of around 45 minutes— CO levels despite minimal sweep gas flow through the ECLS
well within the “golden hour.” Future conflicts with near- system, yet the V and RR could not be reduced low enough
2
20
peer adversaries possessing similar technological capabilities (because of limitations of the SAVe II) to match the ICU ven-
T
as the US and its allies are forecast to render rapid evacuation tilator, resulting in hyperventilation of the animal. The V set-
T
of combat casualties improbable. 21,22 Such realities necessitate ting on the device we were provided for testing was adjustable
small, lighter, and less-complex medical devices able to be in increments of 50mL only, which may present difficulty to
Expeditionary Mechanical Ventilation/Extracorporeal Life Support During Ground Transport | 67